Particle Size Masterclass: Why measure particle size?

Too often, the reason for carrying out a particle size distribution analysis is stated as “for QA”, or “I need the numbers”, or “because my boss says so”, or “for characterization”. Often, we can proceed deep into a project, having acquired huge amounts of data, with no real clarity about what is driving the measurement.

A product flowability or rheology issue is not solved by aggressive dispersion conditions that cannot be mimicked in the plant, as these flow properties are related to the bulk - not dispersed - particle size distribution. Likewise, relating dissolution and bioavailability is best done on a dispersed sample, as most of the surface area will be available to the external continuous phase. Understanding the reasons for making such a measurement leads to the setting of reasonable and achievable product specifications that are in line with the required product performance.